.item-img{ 
	background: url(https://unsplash.it/100/100?random) center center / 100% 100%; 
}

.appPng{
	width: 353px;
	height: 208px;
	width: 100px;
	height: 58.9px;
	background: url(http://house-detective.oss-cn-guangzhou.aliyuncs.com/appPng.png) center center / 100% 100%;
}

.init{
	width: 100vw;
	height: 215.30vW;
	background: url(http://house-detective.oss-cn-guangzhou.aliyuncs.com/init.jpg) center center / 100% 100%;
}